The present invention relates to drip irrigation hoses and to methods for making such hoses.
Drip irrigation hoses are increasingly being used for irrigating various types of plants since they supply the water directly to the root regions of the plants, and therefore are highly conservative of water resources. One type of irrigation hose is constructed by simultaneously extruding a plastic hose and bonding to its inner surface a plurality of emitter elements, or a strip of emitters, spaced longitudinally of the hose for discharging the water at a slow rate via discharge openings formed in the hose. Another type includes a sheet of flexible plastic material formed into a seamed hose, with the emitter elements bonded within the seam, or to another part of the hose, for discharging the water at a slow rate through discharge openings in the hose. The present invention is applicable to both types of drip irrigation hoses.
Examples of drip irrigation hoses of these types are described in U.S. Pat. Nos. 4,196,853; 5,163,622; 5,183,208; 5,203,503; 5,246,171; 5,333,793; 5,522,551; 5,620,143; 5,695,127; 5,785,785 and 6,027,048.
One problem in using drip irrigation hoses is the difficulty in ensuring relatively uniform discharge rates along the length of the hose. This problem is particularly acute where extremely long lengths of the hose are used since the hose itself produces a pressure drop along its length tending to decrease the discharge rate of the emitters at the end of the hose. This sensitivity of the discharge rate to the water pressure is also a problem where the land being irrigated is not flat and even.
Another problem with such drip irrigation hoses is sensitivity to clogging and the difficulty in dislodging clogging particles.
Both of the above problems are addressed by the drip irrigation hoses described in the above-cited patents. Generally, one or both problems is dealt with by providing each emitter element of the hose with a deformable member, such as a deformable membrane, which deforms in response to pressure to provide pressure-compensation. One known drip irrigation hose includes a continuous strip of relatively elastic material bonded to the inner surface of the tube to define a plurality of labyrinths each having an inlet communicating with the interior of the tube and an outlet communicating with an opening through the tube serving as the discharged outlet.
However, drip irrigation hoses are frequently used for only a single season, or for relatively few seasons. Accordingly, the cost involved in producing such drip irrigation hoses is a significant factor in their use. The known drip irrigation hoses addressed to one or both of the above problems are generally relatively costly to manufacture and/or use relative costly materials.
The known drip irrigation hoses also exhibit a tendency to leak water when the hose is not at its normally-operative pressure, e.g., when initially filling the hose or emptying the hose. Such leakage can result in considerable water wastage particularly where the irrigation system is intermittently operated as commonly done today.
The above-cited U.S. Pat. No. 6,371,390, discloses a drip irrigation hose comprising a tube for conducting pressurized water through its interior and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to the tube at longitudinally-spaced locations along its length to define, with an inner surface of the tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet communication with a tube outlet for discharging water from the tube outlet at a slow rate. The labyrinths are defined by a continuous strip of a relatively inelastic material bonded to the inner surface of the tube, and a formation of a relatively elastic material shaped to define a group of teeth for each of the emitter elements producing, with the inner surface of the tube, turbulent flow passageways at each of the longitudinally spaced locations along the length of the continuous strip. That application described a number of constructions of such drip irrigation hoses, as well as methods and apparatus for making such hoses.
The present invention involves further variations in the construction of such drip irrigation hoses and methods of making such hoses. For the sake of brevity, however, the complete description in the above-cited U.S. Pat. No. 6,371,390 is not reproduced herein but rather is incorporated herein by reference.